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How the placenta evolved from an ancient virus

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Re: How the placenta evolved from an ancient virus

#71

It's amazing how quickly people leap to conclusions in the field of evolutionary biology. Fact: a portion of the placenta's protein sequence is very similar or identical to a virus. Unsubstantiated (and pretty wild) conclusion: the placenta is the product of that virus. We would never accept that kind of mythology in software, medicine, law, etc. – why do it here?

You're right, God made the placenta.

Re: How the placenta evolved from an ancient virus

#72
post #44

Earlier quoted context omitted.

Biological immortality is the technical term for organisms which do not die unless killed, or more accurately where rate of mortality from senescence does not increase with chronological age.

I thought the term was negligible senescence?

They're similar but distinct concepts. Negligible senescence means after a point aging doesn't negatively affect the organism. They don't lose reproductive capability or experience functional decline. Imagine being 20 forever.

Biological immortality means after some point mortality rates don't increase with age - you can still grow old, it just won't directly kill you. Biologically immortal organisms don't have a max lifespan, if they're lucky they can just keep on going, but they may be dramatically more feeble than their younger counterparts.

Re: How the placenta evolved from an ancient virus

#73

Earlier quoted context omitted.

Some context: https://sciencebasedmedicine.org/it-was-inevitable-that-anti... Please do not mistake this comment as antivaxx nonsense, the article linked discredits both the theory and the scientists who started it all.

Thank you! Have you found anything that would indicate any level of actual similarities between S protein and syncytine? Beyond both of them being of virus origin and starting with letter S? I couldn't find anything stronger than "german doctors say" which means nothing.

> I couldn't find anything stronger than "german doctors say" which means nothing.

That's all there is to it.

Re: How the placenta evolved from an ancient virus

#74

It's amazing how quickly people leap to conclusions in the field of evolutionary biology. Fact: a portion of the placenta's protein sequence is very similar or identical to a virus. Unsubstantiated (and pretty wild) conclusion: the placenta is the product of that virus. We would never accept that kind of mythology in software, medicine, law, etc. – why do it here?

> conclusion: the placenta is the product of that virus. We would never accept that kind of mythology in software

Seems like a very reasonable hypothesis if that virus is a retrovirus [1]:

> Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses.

> ...not all ERVs may have originated as an insertion by a retrovirus but that some may have been the source for the genetic information in the retroviruses they resemble.

[1] https://en.wikipedia.org/wiki/Endogenous_retrovirus

Re: How the placenta evolved from an ancient virus

#75

It's amazing how quickly people leap to conclusions in the field of evolutionary biology. Fact: a portion of the placenta's protein sequence is very similar or identical to a virus. Unsubstantiated (and pretty wild) conclusion: the placenta is the product of that virus. We would never accept that kind of mythology in software, medicine, law, etc. – why do it here?

> Unsubstantiated

Not really: https://www.liebertpub.com/doi/10.1089/088922299309810

Re: How the placenta evolved from an ancient virus

#76
post #59

Earlier quoted context omitted.

And the thing that distinguishes eggs from sperm is what? The relative size? (Are there no species where they are roughly the same?) Or that the mitochondria come from the egg? Edit: Looks like it's merely relative size, and when neither gamete is bigger biologists throw up their hands. Sort of a bummer that there isn't a more robust definition. https://en.wikipedia.org/wiki/Isogamy

The relative size but also the structure and the process of fertilization. The sperm enters the egg, not the other way around. Mitochondria come from the egg, yes. Also note that sperm vary in shape. Mammalian sperm have the familiar tadpole shape with a flagellum for swimming. Other species, such as nematodes, have ameboid sperm which move along surfaces rather than swimming freely.

> The sperm enters the egg, not the other way around.

I think this is wrong. My understanding is that the sperm cell membrane fuses with the egg cell membrane, forming a single container. The haploid nucleus of the sperm and the haploid nucleus of the egg then fuse. This processes is by no means fully symmetric (the egg has a tough coating on its cell membrane that must be dissolved by the sperm through the Acrosome reaction), but there is also no time when the sperm cell (delineated by its membrane) is inside the egg cell.

https://en.wikipedia.org/wiki/Acrosome_reaction

My point was not that there aren't many correlated asymmetries between eggs and sperm in particular parts of the phylogenetic tree (like mammals) that can be used for distinguishing them. My point was that there seems to be no fundamental asymmetry that applies to all two-sex sexually reproducing organisms; rather, there is a continuum of degree of gamete dimorphism that ends at organisms where there is no principled distinction between sperm and egg (isogamy).

Re: How the placenta evolved from an ancient virus

#77
post #30

It is also being researched how endogenous retroviruses are part of aging. The very rough idea being that at some point long in past a retrovirus became endogenous and provided a pathway for aging increasing the evolutionary rate of that organism, which would then out-compete most of the immortal organisms with time. Something like: https://pubmed.ncbi.nlm.nih.gov/20346965/

Since I had to look it up... endogenous - having an internal cause or origin. - growing or originating from within an organism.

To put it into context: https://en.wikipedia.org/wiki/Endogenous_viral_element

Re: How the placenta evolved from an ancient virus

#78

It's amazing how quickly people leap to conclusions in the field of evolutionary biology. Fact: a portion of the placenta's protein sequence is very similar or identical to a virus. Unsubstantiated (and pretty wild) conclusion: the placenta is the product of that virus. We would never accept that kind of mythology in software, medicine, law, etc. – why do it here?

The parent link is a journalistic version of the information, not the scientific paper(s) with the evidence.

Besides, the closest equivalent in software is:

If you have ~20 lines of code, written twice with the same function (perhaps crossing multiple functions in the same order), written with identical style and syntax, with maybe some variable names being slightly different.

In a copyright case, would you believe that these originate from different authors?

Re: How the placenta evolved from an ancient virus

#79

I'm just realizing that several shark and snake species also give birth to live young, but I don't know whether they have placentas or similar structures. I'm sure they couldn't be homologous to mammal placentas, right? (Certainly not if this article is right about the timeline.) To what extent do viviparous animals converge when it comes to the mother/child interface? So some sharks have placentas, as mentioned in t…

Sharks are viviparous, oviparous and also ovoviviparous. [..] There are over 500 species of shark living in waters around the world and the majority give birth to live young. The remainder are oviparous, meaning they lay eggs. [..] [..]Whale sharks (Rhincodon typus) are the largest species of shark. Although these animals produce eggs, they don't lay them. Instead, the young hatch while still in the female's body and…

Thank you for this link on how sharks give birth. I never thought the subject would be so fascinating.

Also led me to this interesting article on the Basking shark which has an absolutely gigantic mouth for filter feeding plankton.

https://www.nhm.ac.uk/discover/basking-shark-cetorhinus-maxi...

Re: How the placenta evolved from an ancient virus

#80

It's amazing how quickly people leap to conclusions in the field of evolutionary biology. Fact: a portion of the placenta's protein sequence is very similar or identical to a virus. Unsubstantiated (and pretty wild) conclusion: the placenta is the product of that virus. We would never accept that kind of mythology in software, medicine, law, etc. – why do it here?

Former biochemist here. There may be flaws in the study (i haven't read it), but none of what you're gesturing to strikes me as evidence of "jumping to conclusions". A couple thousand basepairs is a row (a fair assumed length for encoding proteins) is plenty enough to draw conclusions about evolutionary provenance, and this is totally common.

For lots of ho-hum reasons that don't require any spectacular justification, you are full of virus DNA -- it's just mostly never mentioned in popsci articles that come under your skeptical lens :)

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